Question

which best describes the nuclear envelope?
a a bilayer that surrounds the nucleus.
b the outside boundary of the nucleus.
c the nuclear covering that controls whats inside the nucleus.
d a double membrane that controls what goes in and out of the nucleus.

Explanation:

The nuclear envelope is a double - membrane structure. It has the function of controlling the movement of substances in and out of the nucleus. Option a only mentions it is a bilayer (which is correct in terms of being a double - membrane but does not mention the function). Option b only describes it as the outside boundary (lacking the key function aspect). Option c says it controls what's inside (not accurate, it controls in - and - out movement). Option d correctly states it is a double membrane and controls what goes in and out.

Answer:

d. A double membrane that controls what goes in and out of the nucleus.